1. Field of the Invention
The present invention relates to an image projection apparatus such as a liquid crystal projector which guides a plurality of colored lights to a plurality of light modulation elements via a polarization conversion element to project the plurality of colored lights from the plurality of light modulation elements.
2. Description of the Related Art
An image projection apparatus which uses a plurality of light sources emitting a plurality of colored lights and a polarization conversion element controlling polarization directions of the plurality of colored lights is disclosed in Japanese Patent Laid-Open Nos. 2002-244211 and 2004-206046.
An image projection apparatus disclosed in Japanese Patent Laid-Open No. 2002-244211, R-light, G-light, and B-light are emitted in sequence from light emitting diodes of R, G, and B (hereinafter, referred to as LEDs). All of the R-light, the G-light, and the B-light are converted into specific polarized lights (for example, S-polarized light) by a polarization conversion element constituted by a plurality of polarization conversion cells. The R-light, the G-light, and the B-light from the polarization conversion element enter one reflective light modulation element in sequence by one dichroic prism and one polarization beam splitter. A full-color image is projected by forming a primary image for each color on the reflective light modulation element in synchronization with turning on the LEDs of R, G, and B, in sequence.
In an image projection apparatus disclosed in Japanese Patent Laid-Open No. 2004-206046, the R-light, the G-light, and the B-light emitted from respective LEDs of R, G, and B in sequence are temporally alternately emitted as polarized lights having polarization directions orthogonal to each other (P-polarized light and S-polarized light) from a polarization conversion element including a plurality of polarization conversion cells. These polarized lights are alternately guided to two reflective light modulation elements for S-polarization and for P-polarization by using one dichroic prism and one polarization beam splitter. A full-color image is projected by forming a primary image in synchronization with S-polarized light and P-polarized light alternately entering the reflective light modulation elements.
However, in an image projection apparatus disclosed in Japanese Patent Laid-Open No. 2002-244211, in order to switch to turn on and off the LEDs of R, G, and B in sequence, compared with the case where all LEDs of R, G, and B are turned on, the brightness of a projected image is extremely reduced, or a color break is generated.
Also in an image projection apparatus disclosed in Japanese Patent Laid-Open No. 2004-206046, because S-polarized light and P-polarized light are alternately emitted from a polarization conversion element, the brightness of a projected image halves, and a color break is generated. Further, because each reflective light modulation element operates at intervals, these use efficiency is bad.